1. Field of the Invention
This invention relates to methods and apparatus for detecting leaks in hollow bodies. The invention has particular application in detecting leaks in the bodies of recreational vehicles. The method includes increasing the air pressure inside the vehicle so that leaks can be located by applying a leak detecting substance, such as soapy water, to the outside of the vehicle, and watching for bubbles which are formed in the soapy water where a leak allows air to emerge.
2. Description of the Related Art
Recreational vehicles, such as campers and motor homes, are susceptible to water leakage. Water leakage can cause extensive damage to the vehicle, especially if it is permitted to continue for a long time. Water which has entered the vehicle through leaks can collect in spaces behind interior paneling, cabinets and the like. The water can rust, rot and otherwise harm the vehicle and its fittings.
Water leaks may be difficult to locate because water can migrate significant distances along the inside surfaces of a vehicle""s shell before the water appears in a visible location. Most interior surfaces in a recreation vehicle are lined or covered with paneling so that it is not possible to easily look for leaks from the inside of the vehicle. Further, it is difficult to recreate the conditions that exist when a vehicle is traveling along a highway while attempting to find leaks. When a vehicle travels at speed certain portions of the vehicle""s exterior experience higher than ambient air pressures. This causes a pressure differential between the vehicle""s interior and exterior which can cause water to be driven into the vehicle. A hole may be large enough to cause a leak when a vehicle is traveling but may be too small to be noticeable from the outside of the vehicle.
It is known that leaks in a vehicle may be located by pressurizing the interior of the vehicle. A leak detecting substance such as a mixture of soap and water can then be applied to the exterior of the vehicle to locate leaks. For example, Canadian Patent Application No. 2,106,951 to Hubert provides a fan mounted to a portable frame which can be placed adjacent to a vehicle. A conduit carries air pressurized by the fan into the vehicle. The conduit passes through a pliable, substantially air impervious member. The air impervious member can be used in various ways to seal an opening through which the conduit enters the vehicle. For example, the conduit may enter the vehicle through a window in a door of the vehicle with the air impervious member inside the door. The outer edge of the impervious member may then be placed between the door and the door frame and held in place by closing the door. The interior of the vehicle can then be pressurized by supplying air through the conduit. The Hubert device can be difficult and time consuming to attach properly and the impervious member is prone to becoming damaged.
After the interior of the vehicle is pressurized air flows outwardly through any faults in the outer shell of the vehicle. Soapy water or another leak detecting fluid can then be applied on the exterior surface of the vehicle. The presence of a leak is indicated by the formation of bubbles in the soapy water.
Schlumbaum, U.S. Pat. No. 3,580,054 discloses apparatus for testing for the presence of leaks in vehicles. The apparatus comprises a portable motor driven suction device which can be placed near a vehicle to be tested. The suction device has a flexible conduit which can be connected to the interior of a vehicle. The suction device can then be turned on. A pressure gauge measures pressure in the interior of the vehicle. If there are leaks in the vehicle then the suction device will be incapable of reducing the pressure inside the vehicle as much as would otherwise be possible. The Schlumbaum device can detect whether or not a vehicle has leaks but is not useful for locating such leaks.
There is a need for an effective leak detecting system which can be quickly and reliably attached to different vehicles.
The invention provides a leak detection method and apparatus. The apparatus comprises an air impeller which can be placed inside a vehicle to draw air into the vehicle. A duct connects the air impeller to an opening in the vehicle, such as a roof vent. One end of the duct has a cuff which seals to a roof vent or other suitable opening. The air pressure inside the vehicle can be raised by drawing air into the vehicle with the impeller. Preferred embodiments of the invention take advantage of the fact that many recreational vehicles have roof vents which are a standard size. This permits the impeller to be readily connected to the roof vent from inside the vehicle. The impeller can then draw air into the interior of the vehicle through the roof vent. Preferred embodiments of the invention provide a cuff which can be attached to the roof vent from inside the vehicle and then attached to the impeller with a flexible conduit. With the conduit detached from the cuff, a person can reach through the cuff to attach the cuff to the roof vent. The cuff may be attached to the roof vent with attachment members which include wide hooks. The hooks can be hooked over the edge of the rim that surrounds standard roof vents as are used on most recreational vehicles sold in North America. The attachment members can then be tightened to secure the cuff against the roof vent.
Another aspect of the invention provides a method of locating leaks in a vehicle having an interior, an exterior surface, and an opening, such as a roof vent. The method comprises: placing an air impeller in the vehicle interior and connecting an inlet of the air impeller to the opening in a substantially air tight manner; closing doors and windows of the vehicle; and, operating the air impeller to draw air into the vehicle interior, thereby raising an air pressure in the vehicle interior to permit leaks to be detected by applying a leak detecting fluid to the exterior surface of the vehicle. Operating the impeller preferably comprises plugging the impeller into an alternating current power outlet built into the vehicle. This avoids the need to have any power cords feed into the vehicle through partially open doors or windows. Preferably the air impeller comprises a variable speed motor and operating the air impeller comprises adjusting a speed of the motor to achieve an air pressure differential in the range of 0.3 inches of water and 1.0 inches of water between the interior of the vehicle and the exterior of the vehicle. Leaks can be detected by applying a soapxe2x80x94water mixture to the exterior of the vehicle and watching for the formation of bubbles. Preferably the opening comprises a square roof vent having a rim on at least two sides and connecting the inlet of the air impeller to the opening comprises attaching a cuff to the opening and connecting the cuff to the air impeller. Attaching the cuff to the opening comprises providing at least one attachment member on the cuff, hooking at least one attachment member over the rim and reducing a length of the attachment member so as to draw the cuff against the opening.